Footwear normally includes an upper and a sole structure. Typically, the upper covers at least part of the shoe wearer foot and secures the foot relative to the sole structure. The sole structure is generally secured to a bottom surface or other portion of the upper and is positioned between the wearer foot and the ground when the wearer is standing. In addition to providing traction, a sole structure may protect a shoe wearer foot and promote wearer comfort.
In particular, many footwear designs rely upon a sole structure to attenuate ground reaction forces and absorb energy as the wearer walks, runs or performs other maneuvers. These sole structure functions, which are sometimes referred to generally as “cushioning,” can be performed using a variety of structures. Often, these structures may take the form of a midsole and/or outsole that is formed from a compressible foam or other similar material. Other energy absorbing structures have included spring-like elements.
Difficulties may arise when designing sole structures for use in footwear intended for specific activities. For instance, some sports and other activities may involve motion that is primarily linear, e.g., walking or running in a generally straight line. For shoes intended for wear during those activities, it may be advantageous to include support and/or cushioning that is concentrated in foot regions that may experience high impact during running or walking. Other activities may involve a significant amount of “cutting” maneuvers in which a shoe wearer moves rapidly to the side. For shoes intended for wear during those activities, it may be advantageous to include additional support and/or cushioning in foot regions that may experience high impact during cutting. Numerous other factors can influence the performance criteria for a shoe design. Such factors can include, without limitation, the hardness of a surface on which the shoe will be worn, differing foot anatomies and preferences of individual shoe wearers. With conventional sole structures, difficulties can often arise when attempting to create or adapt a sole structure design to accommodate a particular activity, user preference and/or other factors.